Engineering Wonders of the World
Volume I

 40 ENGINEERING WONDERS OF THE WORLD. Fig. 15.—A COMPLETE SET OF TURBINES FOR THE “ MAURETANIA ” READY FOR PLACING IN THE SHIP. (Photo, The W allsend Slipway and Engineering Company.) a height of 153 feet above the base line of the ship. The photographs from which the illustrations of the Mauretania s turbines and boilers have been prepared were taken at the works of the Wallsend Slipway and Engineering Company, the constructors of the machinery. We have stated that for high-speed vessels the turbine offers advantages over the piston engine, but when we come to low speeds the position is reversed. The Ration turbine, it is claimed, has of Piston ’ , . . Engines and Proved’ equal or superior m Turbine. economy to the piston engine for speeds down to about 16 knots ; but for vessels below that speed it has, up to the present, been found desirable to adopt the piston engine on account of the greater economy offered. The question of the most economical method of driving slow vessels, however, has recently received the close study of engineers on the Tyne and Clyde and at Belfast, and the opinion is held in many quarters that the solution of the problem lies in a combinatioij of piston engines and a turbine, the former to deal with the high-pressure part of the steam expansion and the latter with the low-pressure part. Mr. Parsons estimated that such a combina- tion would effect a saving of about 12 per cent, in coal, in the case of an intermediate liner of 15 knots speed, over quadruple-ex- pansion piston machinery, and with a reduced weight of propelling machinery ; and in a large vessel of 10 to 12 knots speed a saving of 15 to 20 per cent, in coal consumption over the best triple-expansion piston engines. In some cases there would be an increase of capital cost, which, it was estimated, would be recovered in less than three years by the